Application of Simple Smart Logic for Waterflooding Reservoir Management

A simple smart logic for controlling inflow control valves (ICV) in waterflooding reservoir management is implemented and analyzed, with the final objective of improving the long term financial return of a petroleum reservoir. Such a control is based in a reactive simple logic that responds to the watercut measured in the ICV. Basically, when the watercut increases, the ICV is set to close proportionally. For comparison purposes, four strategies are presented: base case scenario with conventional control, the best completion configuration found by trial-and-error, the reactive control, and a deterministic optimal control based on Nonlinear Gradient Method with adjoint-gradient formulation is shown for comparison purposes. Finally, all four strategies are tested again in different reservoir realizations in order to mimic the geological uncertainties. Two different synthetic reservoir models were studied. First, a simple cube with a five-spot well configuration, in which the permeability field has a horizontal pattern defined by lognormal distributions. The second model is a benchmark proposed by the Dutch university, TU delft, with 101 channelized permeability fields representing river patterns. For the first model, no significant relative gain is found neither in the variable control nor in the optimal control. Manly because of the high homogeneity of the reservoir models. Therefore, no intelligent completion is recommended. On the other hand, for the second and more complex case, the results indicate an expressive relative gain in the use of simple reactive logic. Besides, this type of control achieves results nearly as good as the optimal control. The test in different realizations, however, shows that reservoir characterization is still a key part of any attempt to improve production. Although the variable reactive control is semi-independent, with action being taken based on measurements, some parameters need a priori model to be tuned

Acquired pathological gait patterns and their relationship to structural brain lesions in children with spastic cerebral palsy through Bayesian reasoning: a methodological framework.

Cerebral Palsy (CP) is one of the most common neurological pathologies in children and is caused by a broad range of pre-, peri- or postnataly acquired structural brain lesions, such as periventricular leucomalacia or intraventricular hemorrhage. These brain lesions lead to several topographical involvements (hemiplegia, diplegia, ), primary neuromotor deficits (spasticity, muscle weakness, ) and heterogeneous pathological movement patterns during functional activities, such as walking. The latter has a huge impact on the activities of daily life and consequently patients are often dependent on others. Therapy aiming at the improvement of pathological movement patterns therefore has a socio-economic relevance.Previous research mainly focused on unraveling general connections between brain lesions and motor outcome in children with CP. These studies showed significant relations between (classes of) brain lesions and 1. the (in)ability to walk, 2. a general measure of motor involvement, 3. topographical involvement, 4. muscle tone in premature infants and 5. (classes of) muscle strength. Until now, the relation between pathological movement patterns and brain lesions has not been described. Insight in this connection is crucial for the multidisciplinary treatment of CP as it enables early prediction of movement patterns and individual tuning of the multidisciplinary therapy. The search for relevant connections is hindered by the broad range of brain lesions and the heterogeneity of the gait patterns in CP. Moreover, CP gait is strongly influenced by the primary deficits that interact in a highly complex way. Therefore, it is important to reduce the high-dimensionality of the CP motor data in order to facilitate the search for connections with brain lesions. The overall aim of this PhD was to elucidate the complex relation between the wide range of brain anomalies, primary motor deficits and heterogeneous gait pathologies observed in children with CP (Figure 5) thereby providing a framework for the future construction of a prognostic (Bayesian) model. Such a prognostic model would enable early identification of the main problems in the long term lower limb motor development of children with CP based on brain anomalies, and thus a timely individual goal-setting and tuning of the multidisciplinary therapy. To develop the framework for the future construction of a prognostic (Bayesian) model, this PhD project focused on the development of methodological concepts that allowed (1) modeling of CP gait pathologies; (2) quantifying the role of primary motor deficits in these gait pathologies; and (3) comprehensively evaluating the brain anomalies to further quantify the relation between these anomalies and gait pathology in CP. The crucial aspects and innovations in the field of gait pathology, primary motor deficits and brain anomalies are addressed through several studies, which are outlined below. The first research phase developed a generic workflow for the application of Bayesian reasoning in the preprocessing of three-dimensional gait analysis (3DGA) data. The ultimate goal is the classification of 3DGA data into multiple gait patterns. However, modeling multiple patterns within one patient population (CP) is very complex and Bayesian reasoning has not been applied for this before. Hence, this research phase focused on establishing the methodological workflow for gait classification through Bayesian reasoning and defined the feasibility and efficacy of the Bayesian approach based on a first network modeling the movement patterns of the ankle and knee in the sagittal plane only. A crucial keystone is thereby provided for the future development of a full Bayesian model of CP gait. The second research phase developed high-demand tasks to gain further insight in the role of primary motor deficits in gait. Within this PhD project, a high-demand task for lower limb muscle strength was implemented in the standard 3DGA to assess the added value of this task and to identify 3DGA markers for underlying muscle weakness.The final research phase drafted a standardized and systematic workflow for the collection and analysis of MRI data on brain anomalies. The large set of neurological parameters that resulted from this comprehensive evaluation was then related to the gait pathologies in CP.Table of Contents Dankwoord i Frequently used abbreviations v Chapter 1 General introduction and outline 1 Chapter 2 Probabilistic gait classification in children with cerebral palsy: A Bayesian approach 35 Chapter 3 To what extent is mean EMG frequency during gait a reflection of functional muscle strength in children with cerebral palsy 63 Chapter 4 High-demand tasks to highlight the relationship between muscle weakness and walking in children with cerebral palsy 77 Chapter 5 Macro- and microstructural brain lesions relate to gait pathology in children with cerebral palsy 91 Chapter 6 General discussion 113 Summary 138 Dutch Summary (Samenvatting) 141 Appositions (Bijstellingen) 144 Curriculum Vitae 145 Publications 146nrpages: 148status: publishe

Effect of dynamic orthoses on gait: a retrospective control study in children with hemiplegia

Several positive influences of orthoses on gait in children with cerebral palsy have been documented, as well as some detrimental effects. Most importantly, push-off is decreased in orthoses compromising a physiological third ankle rocker. The aim of this study was to evaluate the effect of three types of orthoses on gait in a homogeneous group of children. All orthoses aimed at improving push-off and normalizing the pathological plantarflexion – knee extension couple. 22 girls and 15 boys with hemiplegia, aged 4-10 years (30 GMFCS 1, 6 GMFCS 2), walked barefoot and with orthoses being either Orteams® (orthoses with dorsal part containing 11 sleeves), Posterior Leafsprings (PLS) or Dual Carbon Fibre Spring AFOs® (CFO; carbon fibre at the dorsal part of the orthosis). All orthoses were expected to prevent plantarflexion and allow dorsiflexion thus improving first, second and third rocker. The latter was expected to improve as energy is absorbed in second rocker, due to the flexibility of the orthosis, and returned in third rocker. The orthoses were compared through objective gait analysis, including 3D kinematics and kinetics. All orthoses successfully improved the gait pattern and only small differences were noted between the different orthoses configurations. The CFO® however, allowed a more physiological third ankle rocker when compared to the Orteam®/PLS. While the PLS ensured the highest correction at the ankle around initial contact, the CFO® created a significantly higher maximal hip flexion moment in stance. In general, the results of this study indicated a substantial functional flexibility of the CFO®.status: publishe

Arm and leg coordination during gait in children with CP and typically developing children

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Is interlimb coordination during walking preserved in children with cerebral palsy?

Arm movements during gait in children with cerebral palsy (CP) are altered compared to typically developing children (TD). We investigated whether these changes in arm movements alter interlimb coordination in CP gait. 3D gait analysis was performed in CP (diplegia [DI]: N = 15 and hemiplegia [HE]: N = 11) and TD (N = 24) children at preferred and fast walking speeds. Mean Relative Phase (MRP, i.e. mean over the gait cycle of the Continuous Relative Phase or CRP) was calculated as a measure of coordination, standard deviation of CRP was used as a measure of coordinative stability, and the sign of MRP indicated which limb was leading (for all pair combinations of the four limbs). In HE, coordination was significantly altered, less stable and a different leading limb was found compared to TD whenever the most affected arm was included in the studied limb pair. In DI, coordination deteriorated significantly when any of the two legs was included in the studied limb pair, and coordinative stability was significantly affected when any of the two arms was included. In almost all limb pair combinations, a different limb was leading in DI compared to TD. Increasing walking speed significantly improved coordination and coordinative stability of several limb pairs in DI. Coordination and limb-leading deficits were mostly linked to the affected limb. The compensating (non-affected) arm primarily affected coordinative stability, which underlines the importance of active arm movements in HE. Increasing walking speed may be used to improve interlimb coordination in DI.status: publishe

A Bayesian network prototype for CP gait classification

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Gait stability in children with Cerebral Palsy

Children with unilateral Cerebral Palsy (CP) have several gait impairments, amongst which impaired gait stability may be one. We tested whether a newly developed stability measure (the foot placement estimator, FPE) which does not require long data series, can be used to asses gait stability in typically developing (TD) children as well as children with CP. In doing so, we tested the FPE's sensitivity to the assumptions needed to calculate this measure, as well as the ability of the FPE to detect differences in stability between children with CP and TD children, and differences in walking speed. Participants were asked to walk at two different speeds, while gait kinematics were recorded. From these data, the FPE, as well as the error that violations of assumptions of the FPE could have caused were calculated. The results showed that children with CP walked with marked instabilities in anterior-posterior and mediolateral directions. Furthermore, errors caused by violations of assumptions in calculation of FPE were only small (≈ 1.5 cm), while effects of walking speed (≈ 20 cm per m/s increase in walking speed) and group (≈ 5 cm) were much larger. These results suggest that the FPE may be used to quantify gait stability in TD children and children with CP

Gait stability in children with Cerebral Palsy

Children with unilateral Cerebral Palsy (CP) have several gait impairments, amongst which impaired gait stability may be one. We tested whether a newly developed stability measure (the foot placement estimator, FPE) which does not require long data series, can be used to asses gait stability in typically developing (TD) children as well as children with CP. In doing so, we tested the FPE's sensitivity to the assumptions needed to calculate this measure, as well as the ability of the FPE to detect differences in stability between children with CP and TD children, and differences in walking speed. Participants were asked to walk at two different speeds, while gait kinematics were recorded. From these data, the FPE, as well as the error that violations of assumptions of the FPE could have caused were calculated. The results showed that children with CP walked with marked instabilities in anterior-posterior and mediolateral directions. Furthermore, errors caused by violations of assumptions in calculation of FPE were only small (≈ 1.5 cm), while effects of walking speed (≈ 20 cm per m/s increase in walking speed) and group (≈ 5 cm) were much larger. These results suggest that the FPE may be used to quantify gait stability in TD children and children with CP.publisher: Elsevier articletitle: Gait stability in children with Cerebral Palsy journaltitle: Research in Developmental Disabilities articlelink: http://dx.doi.org/10.1016/j.ridd.2013.02.011 content_type: article copyright: Copyright © 2013 Elsevier Ltd. All rights reserved.status: publishe

Influence of increased weight on gait characteristics in children with cerebral palsy

SUMMARY Objective of the study was to explore changes in gait patterns caused by artificially enlarging the impact of weakness in children with cerebral palsy (CP). CONCLUSIONS Walking with 10% extra weight in children with CP resulted in reduced walking speed, increased crouch and decreased pelvic ROM. INTRODUCTION One of the primary neurological motor deficits in CP is weakness. Overall moderate correlations were found between lower limb strength and gait data1,2,3,4. Prediction on gait patterns based upon clinical measurements, such as strength evaluation, remains limited5. Manipulating primary neurological deficits, such as weakness, may enable a more precise evaluation and objective quantification of the impact of the deficit on the gait pattern. PATIENTS, MATERIALS AND METHODS Ten children with CP (6 hemi-, 4 diplegia, mean age 8.9 years) were included into this prospective pilot study (inclusion criteria: diagnosis of CP, 5-12 years of age, no history of surgery or recent BTX-A treatment). All children first received full barefoot gait analysis (lower limb kinematics and kinetics, 8 camera vicon system, 2 AMTI force plates, PlugInGait markerset). Subsequently, extra gait trials were collected after indirectly enlarging the impact of weakness on the gait pattern. Muscle strength was therefore relatively reduced by adding 10% weight to the body, by means of a diving belt (lead was fixed to the belt). To avoid asymmetry, the weight was evenly distributed around the waist, close to S-2, which is considered to be the approximate location of the centre of mass. For each patient the gait analysis data of two trials were used. 72 gait parameters per gait trial were compared between the baseline and extra weight condition by one-way ANOVA (with posthoc Tuckey). RESULTS Children with CP who walked with increased weight showed significantly reduced walking speed and a delayed timing of toeoff compared to the baseline condition. Extra weight also caused increased knee flexion at initial contact and an overall more flexed position in stance. Significant changes due to extra weight were also recognized at the hip and pelvis (Table 1). DISCUSSION This pilot study highlighted some changes in gait due to extra weight, which may be considered as parameters that measure the ‘provoked’ weakness. Our conclusions concerning gait parameters that are sensitive to weakness should be tentative as we have a limited number of analysed patients so far. Future analysis in a larger group, including a control group of typical children, and with increased intersubject variability for strength and functional level, can help to recognize patients who walk with a gait pattern that is mainly related to overall weakness. REFERENCES [1] Ross et al. (2007), Arch Phys Med Rehabil 8(8):1114-1120. [2] Damiano et al. (2001), Eur J Neurol 8(5):40-49. [3] Engsberg et al. (2006) Pediatr Phys Ther 18(4):266-275. [4] Morton et al. (2005) Clinic Rehab 19(3):283-289.status: publishe

Is interlimb coordination during walking preserved in children with cerebral palsy?

Arm movements during gait in children with cerebral palsy (CP) are altered compared to typically developing children (TD). We investigated whether these changes in arm movements alter interlimb coordination in CP gait. 3D gait analysis was performed in CP (diplegia [DI]: N = 15 and hemiplegia [HE]: N = 11) and TD (N = 24) children at preferred and fast walking speeds. Mean Relative Phase (MRP, i.e. mean over the gait cycle of the Continuous Relative Phase or CRP) was calculated as a measure of coordination, standard deviation of CRP was used as a measure of coordinative stability, and the sign of MRP indicated which limb was leading (for all pair combinations of the four limbs). In HE, coordination was significantly altered, less stable and a different leading limb was found compared to TD whenever the most affected arm was included in the studied limb pair. In DI, coordination deteriorated significantly when any of the two legs was included in the studied limb pair, and coordinative stability was significantly affected when any of the two arms was included. In almost all limb pair combinations, a different limb was leading in DI compared to TD. Increasing walking speed significantly improved coordination and coordinative stability of several limb pairs in DI. Coordination and limb-leading deficits were mostly linked to the affected limb. The compensating (non-affected) arm primarily affected coordinative stability, which underlines the importance of active arm movements in HE. Increasing walking speed may be used to improve interlimb coordination in DI